The present invention relates generally to handheld power tools, and specifically to combustion-powered fastener-driving tools, also referred to as combustion tools.
Handheld power tools, including but not limited to drills, saws and fastener drivers are provided in a variety of sizes, depending on the application. Often such tools intended for commercial use are provided with heavier, more durable components to withstand more severe operational environments. In some cases, making the tools more durable provides an unintended consequence, in that the tool becomes tiring to hold for extended periods of use. Tool weight is especially important when work is performed at chest height or overhead, such as in the installation of walls, ceilings or overhead utilities.
Combustion-powered tools are known in the art, and one type of such tools, also known as IMPULSE® brand tools for use in driving fasteners into workpieces, is described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,197,646; 5,263,439 and 6,145,724, all of which are incorporated by reference herein. Similar combustion-powered nail and staple driving tools are available commercially from ITW-Paslode of Vernon Hills, Ill. under the IMPULSE®, BUILDEX® and PASLODE® brands.
Such tools incorporate a housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body.
Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original, or pre-firing position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
Conventional combustion fastener driving tools employ straight magazines holding approximately 75 fasteners each. In some operational applications, particularly commercial construction projects, there is a need for a tool which is capable of driving a greater number of fasteners in a shorter period of time. The use of coil magazines with greater fastener capacities is common in electrically or pneumatically powered fastener driving tools, but for various reasons, such magazines have not become acceptable with combustion tools. Reasons for the undesirability of such high capacity magazines in these tools include the additional weight of the fasteners causing premature operator fatigue, and the additional energy required to operate the coil magazine fastener advance has not proved reliable.
Aside from the size of the magazine of conventional combustion tools, the weight, balance and overall ergonomics of conventional tools have not been suitable for high volume commercial construction applications, among others. Often, when such tools are used for high firing rate installations, approaching or exceeding 100 fasteners per minute, tool ergonomics becomes important in maintaining operator satisfaction with the tool. In such applications, the operator holds the tool for driving fasteners into a vertical surface such as wallboard. As such, the longitudinal axis of the combustion engine is generally horizontal or generally parallel to the ground. Since the combustion engine is usually the heaviest component of the tool, it has a tendency to exert a counterforce to the operator's efforts to control the position of the tool against the workpiece. As a result, the tool tends to be top-heavy, which results in operator fatigue after extended use.
In some applications, operators find that opportunities arise for holding the tool with both hands. Such applications include, but are not limited to situations where the tool is held chest-high or overhead for extended periods of time. While auxiliary handles are well known for many types of power tools, they typically are provided in the form of stub-shafts which are fastened to the tool housing to project outwardly. In the case of combustion-powered fastener-driving tools, design factors of weight and balance are more critical, and conventional auxiliary handles have not been widely adopted.
Also, since balance of combustion-powered fastener-driving tools is important for operator satisfaction, and since the combustion engine is relatively heavy, designers have used the handle to locate other tool components such as electronic control modules, batteries and the like. Such placement offsets the imbalance caused by the combustion engine. However, tool imbalance remains an operational factor for the use of combustion-powered tools in commercial applications.
Another design factor related to combustion-powered fastener-driving tools is that tool and/or environmental temperature influences tool performance, including but not limited to the return of the piston to the prefiring position at the end of the firing/fastener-driving operational cycle. Piston return is accomplished through differential gas pressure within the tool's engine, and such gas pressures are influenced by ambient temperature, particularly in exceptionally hot or cold conditions.
An operational factor in the use of combustion-powered tools is that ambient temperature influences tool performance. At lower ambient temperatures, more fuel is needed to obtain desired combustion. However, conventional tools are incapable of adjustment to variations in ambient conditions.
Still another design factor of such tools is the tendency of conventional combustion tools used in commercial construction applications to jam due to close tolerances between the magazine, the nosepiece and the fasteners being fed from the magazine to the nosepiece. Frequent jams increase operator frustration with such tools.
Thus, there is a need for a power tool having a supplemental handle which does not impair the balance, or add significant weight to the tool. There is also a need for a supplemental handle for a combustion-powered tool which is suitable for incorporating tool components, including but not limited to electronics, batteries and/or temperature monitoring devices.